1. Field of the Invention
This invention relates to method and apparatus for braking a wheeled or tracked vehicle and, more particularly, to method and apparatus for implementing a braking force on an intermediate, interior portion of a drive train of an underground mining vehicle to brake the vehicle.
2. Description of the Prior Art
Fluid applied braking systems are well known in the art of wheeled and tracked vehicles. However, in some instances it is desirable for a braking system to include a fail-safe mechanism whereby loss of power to the vehicle or loss of hydraulic fluid pressure to the braking assembly actuates the braking assembly to engage and stop the vehicle. Several examples of known fail-safe braking systems are disclosed in U.S. Pat. Nos. 4,077,500; 4,667,784; 4,018,140; 4,893,879; 5,190,123; and 4,989,703. Other examples of brake equipment specifically adapted for underground mining machinery are disclosed in U.S. Pat. Nos. 3,578,818; 4,196,798; and 4,406,354.
U.S. Pat. Nos. 4,077,500 and 4,667,784 disclose a piston brake arrangement for applying emergency or parking braking pressure to a vehicle axle. In this brake arrangement, a brake piston is urged by a spring into contact with a series of brake discs and plates to apply a braking force to the vehicle wheel hub. During normal movement of the vehicle, hydraulic pressure is maintained to counteract the spring pressure applying the brake. The pressurized fluid biases the springs and prevents them from exerting pressure on the brake piston.
In the event of a loss in fluid pressure or the need for additional braking power, the hydraulic fluid in the brake is vented. The full force of the springs is exerted against the brake piston. In this manner additional stopping power is provided even when the vehicle is not in operation.
U.S. Pat. No. 4,018,140 discloses a system for braking a railed vehicle which is spring applied in a fail-safe manner and can only be disengaged upon pressurization of the system with an appropriate amount of hydraulic fluid. Also, once the fail-safe brake is engaged, if hydraulic pressure cannot be obtained, the fail-safe mechanism can be overcome by manually retracting the spring to allow the vehicle to move.
U.S. Pat. No. 4,893,879 discloses a fail-safe braking system. A wheel is connected by a hub to a rotatable axle and is stopped by operation of the relatively nonrotatable wheel brake. Conventionally in heavy duty materials handling machinery the braking system includes a housing having a wet pack of brake discs and plates. Cooling fluid is packed around the discs and plates to keep them cool during application of the brakes.
A brake piston is axially movable by a set of springs in the housing to engage the brake pack to stop the wheel from rotating. Hydraulic fluid is controllably injected into a chamber positioned opposite the brake piston. Depending upon the amount of fluid injected into the chamber, the braking pressure of the piston is correspondingly reduced. Under normal operation, sufficient fluid is injected to allow the wheel to rotate freely. However, upon application of a foot pedal or loss of fluid pressure in the system, the pressure in the chamber is reduced, causing the springs to force the brake piston into engagement with the brake pack, thereby stopping the vehicle.
U.S. Pat. No. 5,190,123 discloses a fail-safe braking system located in the wheel hub of a vehicle. The braking system includes a spring brake which can be manually engaged or which engages automatically upon a predetermined drop in hydraulic pressure. The walls of the wheel hub define a hub reservoir surrounding the brake components in which hydraulic fluid or oil is circulated to keep the traditional brake plate/disc pack cool during application of the brakes. Initially, a mechanical spring forces the brake components into engagement. Only application of sufficient hydraulic pressure counters the spring and permits the wheel hub to rotate.
U.S. Pat. No. 4,625,837 discloses a pressurized release braking system. A rotating brake disc is restrained from movement by a pair of non-rotatable braking elements acting against the disc. A sealed chamber is formed between the braking elements and is used to release the braking mechanism. Initially, the braking elements are forced against the disc by a series of regularly positioned spring packs. The spring packs exert a constant pressure against the braking elements and the disc, unless opposed.
In the event that movement of the disc is required, a fluid (typically air) is forced into the chamber between the braking elements. The air is injected at such a pressure to counterbalance the effect of the spring packs and force the braking elements to release the disc. Upon venting of the chamber, the braking elements once again act upon the disc, restraining movement.
While each of the above fail-safe braking assemblies have proved to be effective, it has been found in certain circumstances that a braking system acting upon a vehicle drive axle is ineffective, whether due to spatial constraints or other mechanical considerations. Also, it has been found that, although brake assemblies need a certain amount of lubrication to function efficiently, an excess volume of lubrication can cause reduced vehicle performance during non-braking operations.
Therefore, there is a need for a braking system that applies a braking force on an intermediate portion of a vehicle drive train, removed from the vehicle drive axle.
There is further need for a manual disengagement assembly for easily and effectively disengaging a fail-safe braking assembly on an intermediate portion of a vehicle drive train.
An additional need exists for a brake system cooling assembly that reduces the amount of brake lubricant present during non-braking operations.
In accordance with the present invention there is provided a disc braking apparatus for a motor driven vehicle that includes a drive motor. An input shaft is connected to the drive motor for rotating the input shaft at a preselected rate. An intermediate drive mechanism is drivingly connected to the input shaft to transfer rotation from the input shaft at a modified rate. A final drive mechanism is drivingly connected to the intermediate drive mechanism to transfer rotation to at least one wheel of the vehicle. A disc brake assembly is connected to the intermediate drive mechanism for applying a braking force to the intermediate drive mechanism to interrupt rotation transfer to the final drive mechanism and brake the vehicle wheel.
Further in accordance with the present invention, there is provided an underground mining machine that includes a machine frame with a traction mechanism connected to the machine frame for moving the machine frame. A drive motor is mounted on the machine frame for driving the traction mechanism. An input drive shaft is drivingly connected to the drive motor. A brake plate extends from the input drive shaft to rotate therewith. The input drive shaft is longitudinally movable and rotatably mounted on the machine frame. A planetary carrier is drivingly connected to the input drive shaft. The planetary carrier is longitudinally movable relative to the input drive shaft. A drive mechanism is drivingly connected to the planetary carrier for transmitting rotation to the traction mechanism. A brake disc assembly is mounted adjacent to the planetary carrier for movement into frictional engagement with the brake plate to apply a braking force to the brake plate and interrupt rotation of the input drive shaft to stop movement of the traction mechanism. The planetary carrier has a braking surface positioned oppositely of the brake disc assembly. The planetary carrier is longitudinally movable upon application of a preselected force thereto to move the braking surface into contact with the brake disc assembly and displace the brake disc assembly into functional engagement with the brake plate to stop rotation of the input drive shaft.
Further in accordance with the present invention there is provided a method for braking an underground mining vehicle that includes the steps of mounting a drive motor on a mining machine frame. The drive motor is drivingly connected to an input shaft. The input shaft is drivingly connected through a planetary assembly to a traction device for propelling the vehicle. A brake plate extends from the input shaft to rotate with the input shaft. Rotation is transmitted from the input shaft to a planetary carrier of the planetary assembly. The planetary carrier is provided with a braking surface. The brake plate is positioned laterally of the planetary carrier braking surface. A brake disc is positioned between the planetary carrier braking surface and the brake plate for movement into and out of frictional engagement with the brake plate. Actuating longitudinal movement of the planetary carrier relative to the input shaft moves the carrier braking surface into contact with the brake disc to move the brake disc into frictional engagement with the brake plate and interrupt rotation of the brake plate and input shaft to stop movement of the vehicle.
Accordingly, a principal object of the present invention is to provide an improved method and apparatus for braking a wheeled or tracked vehicle.
An additional object of the present invention is to provide a vehicle disc braking assembly whereby the braking force is applied at an intermediate point in a vehicle drive train, removed from the vehicle drive axle.
A further object of the present invention is to provide a failsafe vehicle braking system which is both hydraulically and manually deactivated.
A further object of the present invention is to provide a brake cooling system which cools brake discs without retarding drive transmission.
These and other objects of the present invention will be more completely disclosed and described in the following specification, the accompanying drawings, and the appended claims.